Automatic headlight control

ABSTRACT

Compact, reliable apparatus operating on electronic principles with no electromechanical parts serves two purposes: one, when the engine is running, to turn on the headlights of a motor vehicle automatically when the ambient level of illumination is such that the headlights should be &#39;&#39;&#39;&#39;on,&#39;&#39;&#39;&#39; e.g. at twilight, and, two, to turn the headlights &#39;&#39;&#39;&#39;off&#39;&#39;&#39;&#39; automatically in the event the engine stops running. In another aspect, this invention completely eliminates the headlight switch presently used, and performs identical functions through electronic circuitry. It can be modified to operate in conjunction with a headlight switch. In both cases, undesirable battery drain is avoided since it is impossible to stop the vehicle and have the lights accidentally &#39;&#39;&#39;&#39;on.&#39;&#39;&#39;&#39; The circuitry is so arranged that the lights remain &#39;&#39;&#39;&#39;on&#39;&#39;&#39;&#39; for a predetermined interval following &#39;&#39;&#39;&#39;switching off&#39;&#39;&#39;&#39; of the ignition system.

United States Patent [1 1 4; =2 ian AUTOMATIC HEADLIGHT CONTROL Michael R. Adamian, 149 Tanoak Lane, Naperville, 111. 60540 Filed: Oct. 12, 1972 Appl. No.: 296,954

inventor:

[56] References Cited UNITED STATES PATENTS 3,694,690 9/1972 Shimizu et a]. 315/83 Primary Examinerl-lerman J. Hohauser Attorney-Leonard S. Knox [4 1 Oct. 30, 1973 [57] ABSTRACT Compact, reliable apparatus operating on electronic principles with no electromechanical parts serves two purposes: one, when the engine is running, to turn on the headlights of a motor vehicle automatically when the ambient level of illumination is such that the headlights should be on, e.g. at twilight, and, two, to turn the headlights off automatically in the event the engine stops running. In another aspect, this invention completely eliminates the headlight switch presently used, and performs identical functions through electronic circuitry. .It can be modified to operate in conjunction with a headlight switch. In both cases, undesirable battery drain is avoided since it is impossible to stop the vehicle and have the lights accidentally on. The circuitry is so arranged that the lights remain on" for a predetermined interval following switching off of the ignition system.

8 Claims, 4 Drawing Figures \GNITIDN NAMD MUNDSTABLE I sensor: GATE. 'NVERTER MULTIVIBRATOR mummnou SENSOR EMERGENCY CONTROL SWITCH CIRCUIT HEAD 5 C R LIGHTS PATENTEDUCI so new 3.769.519 SHEEI 10F 2 CR2 R14 T0 R1 IOOV. T

' OUTPUT 0F Q8 N 0 T H *m M ..A V 50 AH 56 U mm 8 AW MT 0| TC C NH R 0U 0 5 MM C C R H m w w m T 6.1 W W ms N W DE mm mm m .1 N Us 0 G H" G an R w m W5 I 1 A uminum HEADLIGHT CONTROL BACKGROUND OF THE INVENTION It is a common shortcoming for the driver of a motor vehicle to be completely oblivious to a slowly darkening sky and fail to turn on the headlights. The hazards thus engendered are obvious. The present invention eliminates any conscious effort on the part of the driver to turn the lights on or off but depends only on the fact that the engine is running and that the ambient illumination is at a level whereat the driver would normally turn on the lights.

In the other aspect, it is recognised that a driver will park his car, turn off the ignition and inadvertently leave the light switch on. If the hiatus is unduly long, the battery will become exhausted. The present invention incorporates means interrelating the ignition system with the circuit controlling the headlights. Thus, if the invention apparatus fails to sense ignition pulses for a predetermined short interval (and the light switch is on), the headlight circuit will be interrupted until such time as ignition pulses are sensed again. Under these circumstances, the operator re-establishes headlight command by running the engine and generating ignition pulses.

SUMMARY OF THE INVENTION The foregoing objects can be attained with the present invention by the use of electronic components capable of being contained in a case of only a few cubic inches capacity. In this way, the package, including a heat-sink, can be installed behind the dashboard and the ambient illumination sensor can be mounted near the windshield in an unobtrusive position, and if the windshield is clean, as it usually is, the light sensitive element will function accurately.

The apparatus comprises an ignition pulse sensor to detect the presence or absence of ignition pulses which are taken from the primary side of the ignition coil, and an illumination sensor to measure the degree of ambient illumination. The output of both sensors is fed to a nand gate and, if the prescribed conditions are met, the output of the gate is inverted and fed as a trigger pulse to a pulse generator, e.g. a monostable multivibrator. The successive ignition pulses trigger the multivibrator which, once triggered, remains triggered due to succeeding trigger pulses which constitute a train shorter ,than the multivibrator output pulse. This latter conditions a control circuit comprising a suitable relay, e.g. a silicon controlled rectifier which, upon conduction, completes a circuit for the headlights.

The factor of ambient illumination is introduced into the circuit as the output of a photoelectric device. Assuming that the level of ambient illumination regains its normal intensity, the photoelectric device is effective, through the circuit to be described, to turn the lights off automatically.

In the event of an emergency and the engine has stopped or has to be stopped, and the lights are to be turned on, an emergency switch can be used to turn the lights on.

Now, if the driver should leave the vehicle with the ignition turned off, absence of ignition pulses leaves the multivibrator untriggered and the resulting output pulse which maintains the headlights on, will turn the lights off." Should the driver wish to park the vehicle with the headlights on, the off condition which would otherwise result from absence of ignition pulses may be negated by using the emergency switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a preferred embodiment of the invention;

FIG. 2 is a schematic showing of the complete system;

FIG. 3 is a schematic showing a preferred form of constantly triggered pulse generator, for example, a modified monostable multivibrator; and,

. FIG. 4 is a pair of graphs showing the relation between input ignition pulses and multivibrator output.

DESCRIPTION OF THE PREFERRED EMBODIMENT Ignition pulses IP are taken off the primary coil of the ignition system of the vehicle and are applied at terminal 10 (FIG. 2). Resistors R1 and R2 constitute a voltage divider. In the example, R1 is 50K ohms and R2 is 5K ohms, so that, based on a voltage at I? of v, the voltage across R2 will be at least 9v for a short time. Since the ignition detector will respond to an input voltage as low as 4v, the voltage division indicated is sufficient. If R1 is 50K ohms or greater, the ignition coil will not be loaded inordinately by the ignition sensing portion of the circuit described. C1, in parallel with R2, together with Zener diode Z1, which acts as a clipper, serves to protect the transistorQZ against otherwise destructive ignition pulses. In the event of a transient ignition pulse,'Zl clips the same to a safe voltage, e.g. 5.2V. The ignition pulses are applied to the base of an NPN transistor, Q2, via the resistor R12. At this point, it is to be noted that all resistors indicated on the drawings as RB are for applying the required forward bias current tothe respective bases of the several transistors and to protect them from noise which might result in false turn-on.

Emitter B02 is connected to the collector CQl of an NPN transistor Q1. The emitter EQI goes to ground. The output of the illumination detector ID, e.g. a photo-darlington connects to base BQl. Should ambient illuminationexceed some predetermined level, Q1 turns off and, vice versa, Q1 turns on when the illumination drops below said level. Thus, if either Q1, Q2, or both are off, base current will flow through Q3 which is operated at saturation. As a result, the input 31 to the multivibrator will be held at ground level and, therefore, the multivibrator output at 32 will be a continuous high. The output at 32 is applied to B04 and Q4 will be biased on. CO4 is connected to the gate of a silicon controlled rectifier SCR so that the SCR remains off.

Since, as shown in FIG. 2, the circuit to the lights (head and tail lights) L,L is completed from B+ through .the SCR, when the latter is non-conductive, the lights remain off, i.e., the ambient illumination is at, or above, the predetermined level.

Typical ignition firing voltages, as viewed from the primary of the ignition coil are approximately 100v, as mentioned previously. The Rl-RZ divider network applies a fraction of the voltage to B02, say about 0.9V. Since Q2 inverts the ignition pulses once, a re-insertion is necessary before the ignition pulse information may be applied to the multivibrator, and this result is obtained through Q3.

At this juncture, it is to be noted that the engine is running (condition one) and that the level of ambient illumination (condition two) has fallen below the predetermined value. Thus, as soon as the multivibrator is triggered by the first ignition pulse, it generates an output pulse (based on parameters to be discussed hereinafter) of 37.5 milliseconds duration. If the engine is at idle speed or above, this time will be sufficient to hold Q4 off for a period of time extending beyond the succeeding ignition pulse. I

Reverting to H6. 4, the ignition pulses are indicated at I]? at an assumed amplitude of 100v. Input to the multivibrator are pulses of sufficient amplitude and the output 32 has a prolonged pulse of zero volts amplitude. 04 turns off which causes the SCR to turn on. Thus, the lights turn on. Since the width of the multivibrator output pulse is designed to be longer than the space between consecutive ignition pulses, the multivibrator remains continuously triggered until one of the two conditions is absent, i.e., the engine is turned off or the ambient illumination reaches or exceeds the predetermined norm.

1 As the ignition pulse repetition rate increases, the period decreases, while the multivibrator pulse width remains constant; the SCR and the headlights are on. In the event 01, Q2 or both turn off, Q3 will turn on which, in turn, causes the lights to be off.

The invention includes provision for allowing the lights to be turned on even though the engine is not running. Thus, in FIG. 2, an emergency switch SE, e.g. a micro-switch or an additional pair of contacts added to the existing emergency switch, with rating of lOma, is arranged to switch on and SE conducts current in the order of Sma. Normally, B05 is grounded and Q5 is off. Under these circumstances, the SCR is controlled by Q4. lf SE is shifted to its alternate position, the SCR is controlled directly by Q5 and the headlights will be turned on, irrespective of the multivibrator output. CR1 blocks the current from CO4 and forces emitter current from O5 to flow into the gate of SCR.

For convenience of understanding, the possible combinations of ambient illumination and engine conditions are tabulated:

Illum. Engine SE 04 SCR Headlights Low Off Off On Off Off High On Off On Off Off Low On Off Off On On High Off Off On Off Off Low Off On On On High On On On 'On Low On On On On High Off On On On The exemplificative circuit thus far described is shown in block form in H6. 1. It is believed that the same will be clear from what has preceded.

Specifications of the components of the exemplificative arrangement of FIG. 2 are asfollows:

illumination Sensor, Motorola Photo-Darlington Amplifier Type 2N5777, or equivalent Z1, Z2, Motorola Type 1N3732, or equivalent SCR, Texaslnstrument Type 2N683A, or equivalent NPN Transistors Motorola Type 2N653 1, or equivalent CR3) Motorola 1N400l or equivalent CR4) C1 0.01 uf C2 0 uf MULTIVIBRATOR The monostable multivibrator MV of FIG. 2 is shown in greater detail in FIG. 3. Rectifiers CR2, CR3, together with resistors R13 and R14 apply the input ignition pulse and illumination intelligence to the bases B06 and BQ9. Normally, Q6 is of and O7 is on.

Therefore, Q8 is ,off, and Q4 is on, which implies the lights are off.

Now, when ignition pulses are sensed at 31, Q6 and Q9 both turn on and capacitor C2 becomes fully discharged. Resistors R13 and R14 avoid current hugging between Q6 and Q9.

When C2 is fully discharged, the voltageat point A, VA, is reduced almost to 0 volts which turns Q7 off. Feedback from Q7 will turn Q6 on and hold'it on for as long as Q7 is off. During thistime, C2 begins to charge for V,, 1.4 v V, 5.2 V." -V-,,,,, V.

R, 25 KO t,= 37.5 m secs. which is longer than any possible period between ignition pulses after or at idle. twill actually be greater than 37.5ms, due to are duration. 3

After the first ignition pulse, Q6 turns on and remains on because C2 is charging. When the second ignition pulse arrives, O6 is unable to change the state of the capacitor, but, in the meantime, Q9 turns on and discharges C2. Consequently, C2 holds V,, 2V where V is the baseto-emitter voltage of Q9, for as long as ignition pulses continue.

It will have become apparent that the time constant R5C2 associated with the circuit can be made extremely long. Consequently, when the last ignition pulse appears the lights will remain on for a period of time defined by the width of the output pulse of the multivibrator which may be on the order of several seconds. Furthermore, the circuit identifies the first ignition pulse, i.e., the leading edge of the monostable wave form, as well as the last iginition pulse, i.e., 1 pulse time prior to the trailing edge of the monostable wave form. It will be clear that, after the last ignition pulse, the lights will remain on for a period of time as directed by the time constant of R5C2.

The apparatus serves its several functions independently of the position of the ignition switch of the vehicle. However, the headlight switch may be incorporated in the invention in two distinct ways;

a. A set of switch contacts maybe introduced between BQZ and ground. These contacts need be rated at only a few milliamperes in contrast to those presently used. When these contacts are closed, Q2 will be off and will still inhibit ignition I pulses. When these contacts are open then ignition pulses will appear across EQ2.

b. 01 and ID may be removed and the set of switch contacts referred to in the preceding subparagraph (a) are introduced between EQ2 and ground. in this case, the functions previously performed by ID are assumed by the driver of the vehicle by controlling the headlight switch. If the mentioned set of contacts is closed, the circuit will function as though D were in the circuit and the ambient illumination had fallen below the predetermined level. If these contacts are opened, the situation would be as if lD were in the circuit and the ambient illumination were high. In brief, by inserting the set of contacts, thefunctions of ID are performed manually.

It will be understood that by choosing a low level of ambient illumination which is still sufficient to activate the apparatus, one may have the headlights come on even during the daytime when the engine is running. In this way, the vehicle will be more readily detectable. in its surroundings.

I claim:

1. Apparatus for controlling the headlights of a vehicle driven by an internal combustion engine including an electrical ignition system, in accordance with an ambient light condition comprising: a photoelectric device responsive to said condition, means connected to the ignition system to provide a train of pulses corresponding at least in periodicity to the firing pulses of the ignition system, circuit means responsive to the output of said device and said pulses jointly, a pulse generator to be triggered by said ignition pulses when said device provides an output corresponding to a low level of ambient illumination justifying an on condition of the headlights and vice versa, the time constant of the pulse generator being so determined as to provide for a length of pulse in excess of the period of the successive ignition pulses and circuit means connected to the output of the pulse generator to control the on and of condition of the headlights.

2. Apparatus in accordance with claim 1 in which the means utilizing the detector output information and the ignition pulse information comprises a pair of transistors, one of said pair being individual to the ignition pulse circuit, and having its base connected thereto, and the other thereof being individual to the detector output circuit and having its base connected thereto, the emitter of the said one transistor being connected to the collector of said other transistor, the collector of the said one transistor being connected to the input of the pulse generator to apply a triggering signal thereto and to provide phase reversal of the signal from said one transistor prior to applying the same as a triggering pulse.

3. Apparatus in accordance with claim 1 further characterized in that the headlight filaments are connected with the power source of the vehicle in a series circuit which comprises a unidirectional current flow device having a gate, the output of the pulse generator being connected. to the gate to control flow of current to the filaments in accordance with the output of the pulse generator.

4. Apparatus in accordance with claim 1 further characterized by an emergency switch to by-pass the output of the pulse generator in the absence of pulses therefrom and to enable manual operation of the headlights independently of the generator output.

5. The combination in accordance with claim 1 in which the duration of said excess is so regulated by the RC constant of the generator as to allow the headlights to remain on after the ignition is switched off.

6. Apparatus in accordance with claim 1 further characterized in that the headlight filaments are connected with the power source of the vehicle in a series circuit with a relay having actuating means, the output of the pulse generator being connected to said means to control flow of current to the filaments in accordance with the output of the generator.

7. Apparatus in accordance with claim 3 in which said device is a silicon controlled rectifier.

8. Apparatus in accordance with claim 1 in which the pulse generator is a monostable multivibrator, the said multivibrator having a pair of input transistors (Q6, Q9) arranged to constitute an or gate by which either transistor can discharge a capacitor (C2), an RC network (R5C2) which defines the pulse width corresponding to a single input pulse, a diode (CR4) connected in series with the base of a transistor (Q7), which requires a higher voltage at the point A which is one junction drop above the base voltage of transistor UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,769,519 Dated October 30, 1973 Invento Rn It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line "re-insertion should read re-inversion Column LL, line 21, "0'' should read 6 line hl, the quantity "-t/R C should read as an exponent;

line b 3, "V'Y should read v line es, t pulse time" should read t pulse time signed and sealed this 30th day of April 1971;,-

(SEAL) Attest:

EDWARD PLFLETCHERJR. C. MARSHALL DANN Attesting Officer Commissionerof Patents F ORM PO-IOSO (10-69) USCOMM-DC 60376-P69 i U.S. GOVERNMENT PRINTING OF IICE I, O3G6-334,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 759, 519 Dated October 30, 1973 Inventor(S Michael R. Adamian It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 61+, "re-insertion should read IG-illVGISiOD.

Column Lt, line 21, O" should read 6 line i l, the quantity --t/R C should read as an exponent;

line 1 t pulse time" should read t pulse time line a Signed and sealed this 30th day of April 197A.

(SEAL Attest:

ED /IARD M .FLLTCHER JR C MARSHALL DAMN Attesting; Officer Commissioner of Patents F ORM PO-105O (10-69) USCOMM-DC 603764 69 0.5. GOVERNMENT PRINTING OFFICE "l9 0-366-334, 

1. Apparatus for controlling the headlights of a vehicle driven by an internal combustion engine including an electrical ignition system, in accordance with an ambient light condition comprising: a photoelectric device responsive to said condition, means connected to the ignition system to provide a train of pulses corresponding at least in periodicity to the firing pulses of the ignition system, circuit means responsive to the output of said device and said pulses jointly, a pulse generator to be triggered by said ignition pulses when said device provides an output corresponding to a low level of ambient illumination justifying an ''''on'''' condition of the headlights and vice versa, the time constant of the pulse generator being so determined as to provide for a length of pulse in excess of the period of the successive ignition pulses and circuit means connected to the output of the pulse generator to control the ''''on'''' and ''''off'''' condition of the headlights.
 2. Apparatus in accordance with claim 1 in which the means utilizing the detector output information and the ignition pulse information comprises a pair of transistors, one of said pair being individual to the ignition pulse circuit, and having its base connected thereto, and the other thereof being individual to the detector output circuit and having its base connected thereto, the emitter of the said one transistor being connected to the collector of said other transistor, the collector of the said one transistor being connected to the input of the pulse generator to apply a triggering signal thereto and to provide phase reversal of the signal from said one transistor prior to applying the same as a triggering pulse.
 3. Apparatus in accordance with claim 1 further characterized in that the headlight filaments are connected with the power source of the vehicle in a series circuit which comprises a unidirectional current flow device having a gate, the output of the pulse generator being connected to the gate to control flow of current to the filaments in accordance with the output of the pulse generator.
 4. Apparatus in accordance with claim 1 further characterized by an emergency switch to by-pass the output of the pulse generator in the absence of pulses therefrom and to enable manual operation of the headlights independently of the generator output.
 5. The combination in accordance with claim 1 in which the duration of said excess is so regulated by the RC constant of the generator as to allow the headlights to remain ''''on'''' after the ignition is switched ''''off.''''
 6. Apparatus in accordance with claim 1 further characterized in that the headlight filaments are connected with the power source of the vehicle in a series circuit with a relay having actuating means, the output of the pulse generator being connected to said means to control flow of current to the filaments in accordance with the output of the generator.
 7. Apparatus in accordance with claim 3 in which said device is a silicon controlled rectifier.
 8. Apparatus in accordance with claim 1 in which the pulse generator is a monostable multivibrator, the said multivibrator having a pair of input transistors (Q6, Q9) arranged to constitute an ''''or'''' gate by which either transistor can discharge a capacitor (C2), an RC network (R5C2) which defines the pulse width corresponding to a single input pulse, a diode (CR4) connected in series with the base of a transistor (Q7), which requires a higher voltage at the point A which is one junction drop above the base voltage of transistor (Q7) to turn transistor (Q7) ''''on'''' which requires higher voltage across capacitor (C2), a feedback network (C3R16), a pair of diodes (CR2, CR3) each connected in series with an individual resistor (R13, R14) to preclude curreNt hugging between the input transistors (Q6, Q9), and a buffer transistor (Q8) connected to the collector of transistor (Q7) through a resistor (R19) connected to the collector of transistor (Q7) to avoid overloading the transistor (Q7) and the feedback network (C3R16). 